In the heat exchanger of the 4-108 I am cleaning up I found what looks like the remains of two screw in anode plugs. One is about 5/8" at the end where the raw water in & out are located. The other is a 1/4" plug that I think was near the end cap where the raw water comes out of one half of the tubing and enters the other half. (I don't have the unit here at the moment) I bought anodes for each, the 5/8" needs to have about half sawed off before it will fit when screwed in.

Questions:

The 1/4" anode has a long, thin zinc about 2.5>3". I kind of wonder about it corroding a bit (doing its job) but breaking off and leaving the chunk stuck in the tubing. Plausible concern? Should I cut it down?

There are three 1/4" plugs on the unit. One in the raw water part and two in the coolant section. Is there any reason to put an anode in the coolant section?

Are there other anodes on the actual,engine block? If so where would I likely find them?

Did you ever get your question answered? I've had my Perkins 4-108 for almost two years and have yet to find any zincs. I have a workshop manual, but there is no mention of any. Just took the heat exchanger to a radiator shop to get it cleaned and saw no evidence of a place for a zinc. This question has been bugging me.

My boat does not have the one in Dag's picture, which is inline on the raw water intake line upstream of the pump. But it looks handy to have such a fitting for winterizing. I might add one in my reassembly.

Here is an exploded diagram of the heat exchager setup that I modified to correct some errors and to indicate anodes:

There is a 5/8" plug which has an anode and as mentioned above, needs to be sawed down to a length that fits. At the other end of the HE is a 1/4" plug which on my unit had the remnants of an anode. So I bought one and put it in there, too. That makes for two anodes in the HE.

Apparently there are no anodes on the block itself. I guess since only coolant/antifreeze runs through the block an anode is not needed.